The invention is based on a minimum-maximum speed governor for fuel-injected internal combustion engines. A speed governor of this kind is already known (German Offenlegungsschrift No. 30 18 720), in which a leaf spring acting as the idling spring rolls off in accordance with rpm on a two-part support bearing provided with a contoured rolloff path; the form selected for the contoured rolloff path produces a spring characteristic such that the idling regulation is stabilized. By means of an adjusting cam actuatable by the adjusting member, the second part of the support bearing, which is supported on the governor housing, can be forced away from the leaf spring when the adjusting member is pivoted into the full-load position, the intended result being to reduce as much as possible the influence of the leaf spring during full-load speed regulation. In this type of minimum-maximum speed governor, it is unnecessary to use an additional idling spring such as is used for instance in a minimum-maximum speed governor of similar design known from German Offenlegungsschrift No. 29 00 198.
With both the known governors, a sufficiently large load increase is possible while the engine speed is dropping, and because of the idling spring as it rolls or by means of the additional idling spring, the P-degree or speed drop is increased in the direction of a higher rpm, so that the engine is "intercepted" when the load is rapidly decreasing and will not stall. In both speed governors, the exertion of force by the idling springs is at least predominantly precluded after the idling sleeve travel distance has been covered, as a result of which, advantageously, these springs either do not influence the speed regulation characteristic curve or else do so only to an insignificant extent. However, despite the improved idling speed regulation attained with them, both known speed governors operating as minimum-maximum speed governors of an injection pump for Diesel vehicle engines have a so-called "start-up weakness", the source of which is the relatively small increase in fuel quantity when the adjusting member has been pivoted out of the idling position. Furthermore, in the known minimum-maximum speed governors no speed regulation takes place between the idling range and the maximum engine speed, except for a torque control which may be provided in some cases. Because of the lack of a regulating function above the idling range until the breakaway point where speed regulation is effected, not only is there reduced engine smoothness, but starting up is more difficult when there is high driving resistance, for instance when engaging the engine while driving uphill; as a result, if the position of the adjusting member (the driving pedal position) is unchanged, the engine can either race up to the maximum full-load speed or "killed", depending on the torque difference. Engine racing causes increased clutch wear, among other effects.